Monitoring during additive manufacturing process using thermocouples

ABSTRACT

A build plate may include one or more thermocouples placed on an underside of the build plate. The one or more thermocouples output temperature fluctuation to assist in monitoring for build plate separation of a product located on top of the build plate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part, and claims priority to andthe benefit of, application Ser. No. 16/299,021, filed on Mar. 11, 2019.The subject matter thereof is hereby incorporated herein by reference inits entirety.

FIELD

The present invention relates to an additive manufacturing process, andmore particularly, to monitoring build plate separation during theadditive manufacturing process.

BACKGROUND

With additive manufacturing process, larger print beds or multi-lasersystems may be used. For example, a build module may include a powderhopper and a build plate chamber. The powder hopper contains metalpowder, which is moved on top of a build plate located within the buildplate chamber. A laser then melts a pattern and this pattern becomes asolid sheet of metal.

With this manufacturing process, only the top layer is exposedpreventing the bottom layer from being seen. As a part is being builtover the course of two to three days, and even longer in some cases, thebottom layer, which is not visible to the naked eye, may become warpedduring this process.

This warpage is referred to as build plate separation due to built upresidual stresses in the part. In one example, significant warpage mayoccur due to large amounts of residual stress. The warpage may ruin thedimensional integrity and usefulness of the part.

Thus, an alternative process for monitoring build plate separation maybe more beneficial to allow a user to stop the manufacturing process,make appropriate changes to the design or parameters of the part, andrestart.

SUMMARY

Certain embodiments of the present invention may provide solutions tothe problems and needs in the art that have not yet been fullyidentified, appreciated, or solved by current monitoring techniques foradditive manufacturing. For example, some embodiments generally pertainto detecting build plate separation of a large three-dimensional (3D)printed part by way of thermocouples.

In an embodiment, an apparatus may include one or more thermocouplesplaced on an underside of a build plate, configured to outputtemperature fluctuation to assist in monitoring for build plateseparation of a product located on top of the build plate.

In another embodiment, an apparatus may include a build plate. On theunderside of the build plate, a plurality of grooves are machined atvarious depths and thermocouples are placed therein to analyzetemperature fluctuations during the additive manufacturing process. Whenthe temperature is abnormal, the additive manufacturing process isstopped to avoid complete build plate separation.

In yet another embodiment, an apparatus may include one or morethermocouples placed on an underside of a build plate and opposite toends of a part to be manufactured. The apparatus may also include one ormore thermocouple readers configured to monitor and record thetemperature observed during an additive manufacturing process of thepart. When the one or more thermocouple readers detect an abnormaldecrease in temperature, the additive manufacturing process is halted toprevent build plate separation.

In yet a further embodiment, a method for performing real-timemonitoring of build plate separation during additive manufacturingprocess includes configuring one or more thermocouples to detecttemperature fluctuations indicative of heat flowing from a part placedon top of a build plate during the additive manufacturing process. Themethod also includes configuring one or more thermocouple readers tomonitor and record the temperature fluctuations from the one or morethermocouples. The method further includes when the one or morethermocouple readers record an abnormal temperature fluctuation from theone or more thermocouples, configuring a computing device configured toidentify the build plate separation from the abnormal temperaturefluctuation and automatically halt the additive manufacturing process inreal-time.

In yet another embodiment, a method for performing real-time monitoringof build plate separation during additive manufacturing process includesdetecting, by one or more thermocouples, temperature fluctuationsindicative of heat flowing from a part placed on top of a build plateduring the additive manufacturing process. The method also includesmonitoring and recording, by one or more thermocouple readers,temperature fluctuations from the one or more thermocouples. The methodfurther includes when the one or more thermocouple readers record anabnormal temperature fluctuation from the one or more thermocouples,identifying, by a computing device, the build plate separation from theabnormal temperature fluctuation, and automatically halting the additivemanufacturing process in real-time.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the advantages of certain embodiments of the inventionwill be readily understood, a more particular description of theinvention briefly described above will be rendered by reference tospecific embodiments that are illustrated in the appended drawings.While it should be understood that these drawings depict only typicalembodiments of the invention and are not therefore to be considered tobe limiting of its scope, the invention will be described and explainedwith additional specificity and detail through the use of theaccompanying drawings, in which:

FIG. 1 is a block diagram illustrating an additive manufacturingmonitoring system configured to monitor for build plate separation,according to an embodiment of the present invention.

FIG. 2A is a block diagram illustrating an underside of build platelocated within the build plate chamber of FIG. 1, according to anembodiment of the present invention.

FIG. 2B is a cross-section diagram illustrating build plate with aplurality of grooves at varying depths, according to an embodiment ofthe present invention

FIG. 3 is a graph illustrating a thermocouple reading of a horizontalrod and a vertical rod, according to an embodiment of the presentinvention.

FIG. 4 is a graph illustrating a non-averaged thermocouple of thevertical rod, according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating a product (or horizontal rod),according to an embodiment of the present invention.

FIG. 6 is an image illustrating horizontal rods with build plateseparation, according to an embodiment of the present invention.

FIG. 7 is a graph illustrating build plate separation with respect toregion 1, region 2, and region 3, according to an embodiment of thepresent invention.

FIG. 8 is a diagram illustrating build plate separation with respect toregion 1, region 2, and region 3, according to an embodiment of thepresent invention.

FIG. 9 is an image illustrating build plate separation of a product,according to an embodiment of the present invention.

FIG. 10 is a graph illustrating thermocouple readings of build plateseparation of a product, according to an embodiment of the presentinvention.

FIG. 11 is a flow diagram illustrating a method 1100 for performingreal-time monitoring of build plate separation during additivemanufacturing process, according to an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 is a block diagram illustrating an additive manufacturingmonitoring system 100 configured to monitor for build plate separation,according to an embodiment of the present invention. In someembodiments, additive manufacturing monitoring system 100 includes abuild module 102 that contains a hopper 104, a build plate chamber 106,and a powder overflow chamber 110. Located within build plate chamber106 is a build plate 108. A more detailed description of build plate 108is described below with respect to FIG. 2

FIG. 2A is a block diagram illustrating a build plate 108 located withinthe build plate chamber of FIG. 1, according to an embodiment of thepresent invention. In this embodiment, FIG. 2 shows an underside ofbuild plate 108, with the machined routing for thermocouples. In someembodiments, the machined routing may be for k-type thermocouples. Buildplate 108 may be made of 4130 steel in some embodiments.

In this embodiment, a plurality of grooves 202 are machined (or milled)into build plate 108. Depending on the embodiment, each groove 202 maybe machined at same or various depths. See, for example, FIG. 2B, whichis a cross-section diagram illustrating build plate 108 with a pluralityof grooves 202 at varying depths, according to an embodiment of thepresent invention. Grooves 202 allow for strategic placement ofthermocouples 204. Thermocouples 204 are connected to one or morethermocouple readers (see item 120 of FIG. 1) by way of thermocouplewires 120. Thermocouple readers in some embodiments may be composed oftwo 4-channel data loggers that monitor and record the temperatureobserved during the additive manufacturing process.

In an embodiment, thermocouples 204 are placed in locations where theproduct is more likely to suffer build plate separation or stress. Buildplate separation or stress may be caused by residual stresses resultingfrom the repeated localized melting and cooling of the built part. Witha product such as a horizontal rod, thermocouples 204 are placed on theunderside of build plate 108. This way, thermocouples 204 are directlyopposite to that of the ends of the product, and may accurately monitortemperature during the additive manufacturing process.

Returning to FIG. 1, hopper 104 includes metal powder, for example. Thismetal powder is moved into build plate chamber 106. For example, whenhopper piston motor 114 pushes the metal powder up and out of hopper104, a re-coater arm 116 is configured to move the metal powder intobuild plate chamber 106, and more specifically, onto build plate 108.Any excess metal powder may then flow into powder overflow chamber 110for collection. As the metal powder sits on top of build plate 108,laser 118 may melt a pattern in a new layer, on top of build plate 108.For each pass, build plate piston motor 112 lowers build plate 108.

However, while the product manufacturing process is underway, buildplate separation cannot be determined until the end of the manufacturingprocess. To cure this deficiency, and to monitor for a stress within theproduct manufactured within build plate chamber 106, one or morethermocouple readers 120 are connected by way of thermocouple wires 122to the underside of build plate 108. In some embodiments, build plate108 is a stainless steel plate. Build plate 108, however, is not limitedto a stainless steel plate and may be composed of any appropriate metalmaterial for selective laser melting.

Upon detection of build plate separation by thermocouple readers 120,the additive manufacturing process may automatically cease by way of acomputing device or may manually shut off. This allows an engineer toadjust the parameters for the additive manufacturing process to preventor mitigate against any defects within the product. Alternatively, theprocess may be aborted to avoid additional cost as loss of time.

To route thermocouple wires 122 from beneath build plate 108,thermocouple wires 122 are fed into overflow chamber 110 and out throughthe overflow chamber 104, which captures unused metal powder. Adequatelength is provided to thermocouple wires 122 to ensure that thermocouplewires 122 are fed continuously to build plate 108 as build plate 108,including thermocouple wires 122, moves for the entire build duration.During this process, thermocouple wires 122 continuously transmit datato the thermocouple readers 120, located outside of the build module102.

FIG. 3 is a graph 300 illustrating a thermocouple reading of ahorizontal rod 304 and a vertical rod 302, according to an embodiment ofthe present invention. In graph 300, plot 302 shows that when theadditive manufacturing process begins for a vertical cylinder, thetemperature sharply increases. The temperature then reaches a plateau,followed by a gradual cooling period. In terms of the laser, the sharpincrease in temperature shows that at the beginning of the process, themelt pool resulting from the laser is close to the thermocouple. As thepart being built increases in height, the distance between the melt pooland the thermocouple gradually increases. The rate of increase intemperature, as detected from the bottom of the build plate, graduallydecreases.

Continuing with the vertical cylinder, FIG. 4 is a graph 400illustrating a non-averaged thermocouple of the vertical rod, accordingto an embodiment of the present invention. In graph 400, plot 402 showspeaks and valleys. The peaks represent when the melt pool is directlyabove the thermocouple as the laser is burning a new layer and thevalley represent the cooling that results from the laser moving to adifferent spot and brief stoppage to allow for the hopper and there-coater arm to deposit a new powder layer onto the build plate.

Returning to FIG. 3, with high residual stress, some parts such as thehorizontal rod is bent and separates from the build plate. In FIG. 3,plot 304 shows a temperature drop in region 306. This temperature dropcorresponds to the build plate separation during the additivemanufacturing process. Normally, the temperature of the build plate isnot monitored during the additive manufacturing process, and therefore,build plate separation may go undetected until the additivemanufacturing process is complete. By monitoring the temperature inrelation to plot 304 of FIG. 3, build plate separation may be detectedsooner than expected.

FIG. 5 is a diagram illustrating a product (e.g., horizontal rod) 500,according to an embodiment of the present invention. This embodimentshows that cooling creates internal tensile force near top surface ofproduct 500. While the free surface at the top of the product 500 isallowed to cool, the internal parts and bottom of product 500 remainshot. The expansion and contraction resulting for this heat gradientcontributes to a constant buildup of internal residual stresses. The netforce, however, may cause one or more edges of product 500 to curlupwards, thereby separating the edge of product 500 from the buildplate.

FIG. 6, which is an image 600, illustrates build plate separation forproducts (a)-(d). In this image, products (a)-(d) show significantamount of lift from the build plate around the edges of products, wherethe stress would be the highest.

FIG. 7 is a graph 700 illustrating build plate separation with respectto Region 1, Region 2, and Region 3, according to an embodiment of thepresent invention. The plot represents data from four differentthermocouples, TC1 — TC4. While the temperature fluctuation measured byeach thermocouple TC1 — TC4 differed, they all exhibited a similartemperature drop as that shown in region 306 of FIG. 3. In all cases,the drop was correlated a build plate separation.

FIG. 8 is a diagram illustrating build plate separation with respect toRegion 1, Region 2, and Region 3 in FIG. 7, according to an embodimentof the present invention. In this embodiment, separation of product 802from build plate 804 is shown in phases with respect to Region 1, Region2, and Region 3. In Region 1, product 802 continues to stay attached tobuild plate 804. Also, in Region 1, good thermal conductivity is shownfrom the top of product 802 through build plate 804 and thermocouple806.

In Region 2, however, warpage of product 802 begins to occur, resultingin lost coupling. Specifically, residual stress within product 802begins to break the ends of product 802 from build plate 804, slowlydeteriorating the connection. Also, in Region 2 (see FIG. 7), overalltemperature begins to decrease rapidly as heat distribution is lesslocalized around the locations of thermocouple 806.

While Region 2 represents the onset of separation, Region 3 representsthe end (or arrest) of the separation. The drop in temperatures detectedby thermocouples 806 stops. Build plate 804 comes to a steadytemperature, which in turn shows complete separation of the end ofproduct 802 from build plate 804. In this region, the temperaturedetected by thermocouples 806 is the result of the overall heating ofbuild plate 804 as heat moves through middle of product 802 and intobuild plate 804, far away from the locations of thermocouples 806.

FIG. 9 is an image 900 illustrating build plate separation of a product902, according to an embodiment of the present invention. In thisembodiment, item 904 represents build plate separation of the initialstructure of product 802. Through a height measurement correlated tothermocouple data, the end of this region is marked by square 1004 onplot 1002 of FIG. 10. Item 906 represents the gradual detachment ofproduct 902 from the build plate, and item 908 represents the steadybuilding of the latter half of product 902 after movement due toseparation, the onset of which is marked by circle 1010.

Should there be no separation, the profile of the product is expected tohave a vertical line with respect to the build plate. Therefore, segment904 in FIG. 9 was vertical prior to separation. Also, in FIG. 9, segment906 was built while the separation continued to happen. Conversely,segment 908 was built after the separation came to an end, andtherefore, a vertical profile appeared with respect to the build plate.

Considering the length of time it took to build the entire part andrelative lengths of segments 904, 906, and 908, the times for the onsetand arrest of the separation (beginning and end of segment 906) wereestimated and shown as squares 1004 and 1008, respectively. In FIG. 10,the circles indicated by 1006 and 1010 represent points in time wherechanges in the temperature profile (or slope of the curve) can bemeasured to indicate the onset and arrest of the separation.

Signal Processing Techniques for Monitoring Temperature Drops During theManufacturing Process

In some embodiments, proper signal analysis techniques are utilized toaccurately quantify the behavior of the additive manufacturingmonitoring system as the product is being built layer by layer. Forexample, the temperature trendline may better address the quality of theadditively manufactured product during the manufacturing process. Anysharp decreases in the trendline are indications of the productseparating during the manufacturing process. When the product separates,inert gas or powder is filled between the product and the build plate.This may result in a large thermal impedance between the laser on topand the thermocouple below the build plate. The large thermal impedancemakes it more difficult for heat to transfer between the laser and thethermocouple, which results in a temperature drop. The thermocoupleessentially reads the build plate's temperature at this point, withlittle to no sensitivity to the laser scans on the part above. Heat isconducted laterally to the center of the part where it is stillconnected, and then through the build plate to the thermocouple wire,rather than straight down through the part and build plate to the wire.The temperature drop rate during separation is much greater than thetypical drop rate during the normal manufacturing process, where thethickness of the part continues to increase and increasingly separatesthe laser from the thermocouple.

However, the signal processing techniques should determine thetemperature trendline in the presence of the following phenomena:

-   -   temperature spikes indicating the melting spot being closest to        the thermocouple    -   temperature spikes appearing at irregular intervals depending on        the randomized melt pattern and part geometry    -   spikes are followed by quick cooling as the next layer of raw        material is swept across    -   5 minute cool down during periodic machine rest periods

The phenomena listed above may cause great difficulty in obtaining thetemperature trendline since it causes what may be considered as highnon-zero mean noise. Adaptive filtering, Kalman filtering,curve-fitting, n-point splines, and more may be used to determine thetrendline in the presence of this noise. Different classifiers may thenbe used on the trendline to determine at least the 2-state problem:normal build or broken part; however, additional states may beconsidered in practice.

In an embodiment, an apparatus may include one or more thermocouplesplaced at predetermined locations on an underside of a build plate tomonitor temperature fluctuations of the build plate during the additivemanufacturing process. When the one or more thermocouples outputabnormal temperature fluctuation, additive manufacturing parameters areadjusted to avoid production of a faulty product, or the additivemanufacturing process is halted to avoid complete build plate separationof the product located on top of the build plate.

In another embodiment, an apparatus may include a plurality of groovesmachined on an underside of a build plate to allow strategic placementof one or more thermocouples. The one or more thermocouples outputtemperature fluctuation to assist in monitoring for build plateseparation of a product located on top of the build plate.

In yet another embodiment, an apparatus may include a plurality ofgrooves machined on an underside of a build plate to allow strategicplacement of one or more thermocouples. The one or more thermocouplesoutput temperature fluctuation to assist in monitoring for build plateseparation of a product located on top of the build plate.

FIG. 11 is a flow diagram illustrating a method 1100 for performingreal-time monitoring of build plate separation during additivemanufacturing process, according to an embodiment of the presentinvention. In some embodiments, at 1105, method 1100 includesconfiguring one or more thermocouples placed to detect temperaturefluctuations indicative of heat flowing from the part placed on top ofthe build plate during the additive manufacturing process. At 1110, themethod also includes configuring one or more thermocouple readers tomonitor and record the temperature fluctuations from the one or morethermocouples. At 1115, the method further includes, when the one ormore thermocouple readers record an abnormal temperature fluctuationfrom the one or more thermocouples, configuring a computing deviceconfigured to identify the build plate separation from the abnormaltemperature fluctuation and automatically halt the additivemanufacturing process in real-time.

The abnormal temperature fluctuation is a temperature drop from the heatflowing from the part placed on top of the build plate during theadditive manufacturing process. See, for example, FIG. 3, whichillustrates a temperature drop at 306. The temperature drop may bedefined by a drop rate in temperature that exceeds an ideal temperaturecool down rate for the part based on a geometry of the part. Forexample, the temperature drop is defined by a drop rate in temperaturethat exceeds an ideal temperature cool down rate for the part asexpressed by the following if

${\frac{T_{t + 1} - T_{i}}{\Delta t} > {STD}},$

then the additive manufacturing process is aborted,

where T is a preconditioned temperature signal being a baseline signalwhere upward temperature spikes from melting spots are removed anddownward temperature spikes for rest periods are removed, At is anamount of time between temperature measurements, i is a measurementpoint in time, and STD is a threshold determined by the part's geometry.

It will be readily understood that the components of various embodimentsof the present invention, as generally described and illustrated in thefigures herein, may be arranged and designed in a wide variety ofdifferent configurations. Thus, the detailed description of theembodiments, as represented in the attached figures, is not intended tolimit the scope of the invention as claimed, but is merelyrepresentative of selected embodiments of the invention.

The features, structures, or characteristics of the invention describedthroughout this specification may be combined in any suitable manner inone or more embodiments. For example, reference throughout thisspecification to “certain embodiments,” “some embodiments,” or similarlanguage means that a particular feature, structure, or characteristicdescribed in connection with the embodiment is included in at least oneembodiment of the present invention. Thus, appearances of the phrases“in certain embodiments,” “in some embodiment,” “in other embodiments,”or similar language throughout this specification do not necessarily allrefer to the same group of embodiments and the described features,structures, or characteristics may be combined in any suitable manner inone or more embodiments.

It should be noted that reference throughout this specification tofeatures, advantages, or similar language does not imply that all of thefeatures and advantages that may be realized with the present inventionshould be or are in any single embodiment of the invention. Rather,language referring to the features and advantages is understood to meanthat a specific feature, advantage, or characteristic described inconnection with an embodiment is included in at least one embodiment ofthe present invention. Thus, discussion of the features and advantages,and similar language, throughout this specification may, but do notnecessarily, refer to the same embodiment.

Furthermore, the described features, advantages, and characteristics ofthe invention may be combined in any suitable manner in one or moreembodiments. One skilled in the relevant art will recognize that theinvention can be practiced without one or more of the specific featuresor advantages of a particular embodiment. In other instances, additionalfeatures and advantages may be recognized in certain embodiments thatmay not be present in all embodiments of the invention.

One having ordinary skill in the art will readily understand that theinvention as discussed above may be practiced with steps in a differentorder, and/or with hardware elements in configurations which aredifferent than those which are disclosed. Therefore, although theinvention has been described based upon these preferred embodiments, itwould be apparent to those of skill in the art that certainmodifications, variations, and alternative constructions would beapparent, while remaining within the spirit and scope of the invention.In order to determine the metes and bounds of the invention, therefore,reference should be made to the appended claims.

1. A method for performing real-time monitoring of build plateseparation during additive manufacturing process, comprising:configuring one or more thermocouples to detect temperature fluctuationsindicative of heat flowing from a part placed on top of a build plateduring the additive manufacturing process; configuring one or morethermocouple readers to monitor and record the temperature fluctuationsfrom the one or more thermocouples; and when the one or morethermocouple readers record an abnormal temperature fluctuation from theone or more thermocouples, configuring a computing device configured toidentify the build plate separation from the abnormal temperaturefluctuation and automatically halt the additive manufacturing process inreal-time, wherein the abnormal temperature fluctuation is a temperaturedrop from the heat flowing from the part placed on top of the buildplate during the additive manufacturing process, the temperature drop isdefined by a drop rate in temperature that exceeds an ideal temperaturecool down rate for the part based on a geometry of the part.
 2. Themethod of claim 1, wherein the build plate comprises a plurality ofgrooves machined on the underside of the build plate to allow forstrategic placement of the one or more thermocouples.
 3. The method ofclaim 1, wherein each of the plurality of grooves have same or varyingdepths.
 4. The method of claim 1, wherein the one or more thermocouplesare connected to one or more thermocouple readers via one or morethermocouple wires.
 5. The method of claim 4, further comprising:configuring the one or more thermocouple readers to monitor and recordtemperature observed during the additive manufacturing process.
 6. Themethod of claim 4, wherein the one or more thermocouple wires are routedfrom the one or more thermocouple readers to the underside of the buildplate.
 7. The method of claim 6, wherein the one or more thermocouplewires are fed into, and out through, an overflow chamber.
 8. The methodof claim 7, further comprising: configuring the one or more thermocouplewires to continuously transmit data from the one or more thermocouplesto the one or more thermocouple readers during movement of the buildplate.
 9. The method of claim 1, wherein the placement of the one ormore thermocouples is determined where the part is more likely toencounter build plate separation or stress.
 10. The method of claim 1,further comprising: automatically aborting the additive manufacturingprocess, when the temperature drop is as follows if$\frac{T_{t + 1} - T_{i}}{\Delta t} > {STD}$ where T is a preconditionedtemperature signal being a baseline signal where upward temperaturespikes from melting spots are removed and downward temperature spikesfor rest periods are removed, At is an amount of time betweentemperature measurements, i is a measurement point in time, and STD is athreshold determined by the part's geometry.
 11. A method for performingreal-time monitoring of build plate separation during additivemanufacturing process, comprising: detecting, by one or morethermocouples, temperature fluctuations indicative of heat flowing froma part placed on top of a build plate during the additive manufacturingprocess; monitoring and recording, by one or more thermocouple readers,temperature fluctuations from the one or more thermocouples; and whenthe one or more thermocouple readers record an abnormal temperaturefluctuation from the one or more thermocouples, identifying, by acomputing device, the build plate separation from the abnormaltemperature fluctuation, and automatically halting the additivemanufacturing process in real-time, wherein the abnormal temperaturefluctuation is a temperature drop from the heat flowing from the partplaced on top of the build plate during the additive manufacturingprocess, the temperature drop is defined by a drop rate in temperaturethat exceeds an ideal temperature cool down rate for the part based on ageometry of the part.
 12. The method of claim 11, wherein the buildplate comprises a plurality of grooves machined on the underside of thebuild plate to allow for strategic placement of the one or morethermocouples.
 13. The method of claim 11, wherein each of the pluralityof grooves comprising same or varying depths.
 14. The method of claim11, wherein the one or more thermocouples are connected to one or morethermocouple readers via one or more thermocouple wires.
 15. The methodof claim 14, further comprising: monitoring and recording, by the one ormore thermocouple readers, temperature observed during the additivemanufacturing process.
 16. The method of claim 14, wherein the one ormore thermocouple wires are routed from the one or more thermocouplereaders to the underside of the build plate.
 17. The method of claim 16,wherein the one or more thermocouple wires are fed into, and outthrough, an overflow chamber.
 18. The method of claim 17, furthercomprising: continuously transmitting, by the one or more thermocouplewires, data from the one or more thermocouples to the one or morethermocouple readers during movement of the build plate.
 19. The methodof claim 11, wherein the placement of the one or more thermocouples isdetermined where the part is more likely to encounter build plateseparation or stress.
 20. The method of claim 11, further comprising:automatically aborting the additive manufacturing process, when thetemperature drop is as follows$\frac{T_{t + 1} - T_{i}}{\Delta t} > {STD}$ if where T is apreconditioned temperature signal being a baseline signal where upwardtemperature spikes from melting spots are removed and downwardtemperature spikes for rest periods are removed, Δt is an amount of timebetween temperature measurements, i is a measurement point in time, andSTD is a threshold determined by the part's geometry.